This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The goal of this study is to test the GM-CSF DNA as an adjuvant for our DNA/MVA SIV vaccine for protection against a pathogenic SIV infection in rhesus macaque. Our previous studies showed that a GM-CSF-adjuvanted DNA/MVA SHIV89.6 vaccine enhances protection against an intrarectal SHIV-89.6P (CXCR4 tropic) challenge in rhesus macaques. GM-CSF appeared to contribute to protection by enhancing the avidity of anti-Env Ab and generating long lasting anti-viral IgA response in rectal secretions. The vaccine regime consists of two DNA inoculations on weeks 0 and 8, followed by two MVA booster immunizations on weeks 16 and 24. GM-CSF DNA is included in cis with DNA/SIV vaccine. The following immunological responses are being monitored: 1) maturation, activation and lymph node homing of dendritic cells, 2) frequency, breath and polyfunctionality of T cell responses in blood and gut and 3) titers and avidity of binding Ab, frequencies of antibody secreting cells (ASC), titer of neutralizing Ab and rectal IgA. The monkey trial is on going and we just boosted the animals with first MVA. So far, we have found that GM-CSF promotes the up regulation of CD86 expression on myeloid DC and CCR7 on monocytes. GM-CSF also promoted the appearance and magnitude of ASCs. These data suggested that GM-CSF co-delivered with SIV vaccine DNA could support the differentiation and maturation of dendritic cells, monocytes as well as B cells. We will challenge these macaques with a pathogenic SIV challenge six months after the last MVA immunization.